Something is not right. HW diagnostics sound like a good idea. WRT MIDI connections check this http://www.emusician.com/...id=273&EntryId=962
 

I would not blame the install of Sonar until trying a LOT of other things that you could try.
 
First off that list of connected gear. Pull it all out. If your lucky and everything works fine then plug things in one at a time until the culprit is found. The iconnect midi is a new device on the market and may be the source for example. Don't know why, but if your audio driver is having a bad day it might cause this.   
 
I would have stopped the export after 4 or 5 minutes because that would be the longest time I have ever seen on a 4 minute song. And I never freeze anything, 16 to 25 tracks and I'll have 4 or 5 soft synths live. So something is terribly wrong there.
I have heard of one certain plug in causing this to happen but as I understand it you have everything bounced and have removed all plug in's and soft synths? If not you'll have to look there for a problem child.
 
 
Other issue is if your hard drive is acting up, Just do a save as to a different hard drive, open the project, if it runs fine then try exporting and to anywhere but that original drive.
 
And what's with the "what you hear" option Isn't that for on board sound cards? Mine exports from my master / Focusrite 1/2 outputs. I use what ever Sonars default setting was but change the bits from 32 to 16 for CD.

Using a few strategies recommended here - thank you all - I am back in business.
I exported one track at a time until I encountered the track that was stalling the export of the whole. It turns out my vocal harmony track was the problem. I discovered a single clip that had a graphical wave representation that didn't match the actual content of the clip. An obvious glitch, I investigated further. The clip wouldn't bounce nor trim. Remembering that at some point in the past I had worked the clip in Melodyne Editor and later in Audiosnap I surmised that some data must have gotten corrupted in the handoff between the two protocols. Hey- it's the best explanation I have. For giggles, I turned Audiosnap on then off again for the clip. The waveform preview suddenly displayed correctly, the clip could be bounced, and the whole project was exported as desired with a Fast Bounce taking only about 30 seconds.
Woohoo!

glad you found it. and you learned to troubleshoot by eliminating things that were not responsible until you found the one that was!
 
a side note: no matter what fx you have on a project, if you uncheck fast bounce and check [hear it, not at my daw] you should be able to listen to the song as it renders, meaning that it won't take longer than the length of the tune.